There has been provided a system which allows multiple people to see an image sensed by a camera provided at a remote location via a network, as well as enables the people to remotely control the pan and tilt angles or zoom magnification of the camera. For example, there has been developed a system which, by connecting a computer-controllable camera via a WWW server on the Internet to a personal computer also connected to the Internet, not only delivers real-time images taken by the camera to a user who has accessed to the system but also allows control of the camera (see Japanese Patent Laid-Open No. 10-040185, for example). The image-delivering side and the image-viewing side are in a server-client relationship.
In such a system which allows controlling of a camera and delivers images to multiple people at multiple locations, operation and observation are assumed to be performed by an unspecified number of users (clients). When a camera (server) is controlled by many people, authorization to control the camera is important (see Japanese Patent Laid-Open No. 10-042278, for example). A client who has acquired the authorization can control the camera. The authorization is released when a predetermined time period has elapsed.
In such a system, multiple levels of authorization are provided, and a higher level user (client) is given higher priority authorization when the user (client) controls the camera. It is disclosed that a different authorization time period is given to each of multiple priority levels (see Japanese Patent Laid-Open No. 10-164554, for example).
Such a system is not only used as a Web camera system, e.g., for the purpose of delivering appearances of sightseeing spots and roads and the like to an unspecified number of people over the Internet, but also often used as a security camera system, e.g., for the purpose of delivering images to particular people for crime prevention and the like.
When such a system is used for monitoring for the purpose of crime prevention, the image is not always seen by someone. Accordingly, in a conventional general monitoring system using an image, the image is continuously recorded so that the recorded image may be later checked in case any abnormality happens. Alternatively, by detecting an abnormality from motions of an image, the image is recorded or abnormality detection information is notified only when such an abnormality is detected.
In such a system allowing multiple people at multiple locations to view an image and enabling only one user at a time to control the camera by giving authorization to him/her as described above, the system administrator and a person who controls the camera are not always the same. For example, a camera may be used as a Web camera for delivering images to an unspecified number of people via the Internet during the day, and as a security camera directed to a particular direction for monitoring to detect an abnormality, such as trespass.
In this case, there is a possibility that an abnormality cannot be detected because an unexpected client has accessed the system and freely controlled the camera. Especially, when the camera is set to record abnormity detection results in an unwatched and automated operation, if the camera is controlled to be changed and fixed to face a direction different from the direction to be monitored or a different zoom magnification, it cannot perform the predetermined abnormality detection, and this may cause a serious problem.